Ok so the central information pathway in a cell is known as the “central dogma” of molecular biology, and it says that the sequence of nucleotides in DNA are first “transcribed” into RNA and then “translated” into a protein. The process that “transcribes” the DNA into RNA is much more straightforward than the process that “translates” RNA into proteins. There is general consensus that life probably began with RNA as the exclusive information carrying molecule. DNA, however, is much more stable and lasts longer in water than does RNA and this probably constituted the rationale for selecting the DNA structure once it emerged through the randomizing directive to increase configurational entropy. The translation mechanism, however, is the genuine mystery which still confronts origin of life theory today.
Here are the 20 natural amino acids, the monomer units of protein polymers:
And here are the four nucleotide bases of DNA: